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Heat waves have an increasing tendency to linger over the same region, which exacerbates their dangerousness, according to a new study, which points the finger at the responsibility of climate change.
While previous research has focused on the frequency and intensity of heat waves, few have so far looked at their propagation in both space and time.
But heat waves, like storms or other weather phenomena, move, Wei Zhang, one of the co-authors of the study, published in the journal Science Advances, told AFP.
But in recent decades, heat waves have tended to “move less and less quickly“, he explained. “This means that they can stay in a region for longer”, which can have “significant consequences for the population“.
Researchers analyzed heat waves globally, over a period from 1979 to 2020, using models based in particular on observations from weather radars and satellites.
Their analyzes showed that each decade, the speed of heat waves had decreased by about 8 km per day.
They also observed that the average duration of heatwaves increased from around 8 days in the early 1980s to 12 days at the end of the period studied.
Their study also showed that heat waves were traveling further than before, and confirmed the increase in the frequency of such events.
The researchers then examined the role of climate change in these changes. To do this, they used climate models to simulate two scenarios — with and without greenhouse gas emissions — and compared them with the actual behavior of heat waves.
“It is quite clear to us that the dominant factor here to explain this trend is anthropic“, or “greenhouse gases” from human activities, said Wei Zhang of Utah State University.
He said he was particularly worried about the cities where these heat waves occur, which may lack greenery or cooler places for disadvantaged populations, for example not being equipped with air conditioning.
“Heat waves traveling farther and moving slower will have more devastating consequences on nature and society in the future if greenhouse gases continue to increase“, concludes the study.